Multiwave variable resonator



' Filed Jan. 10, 1959 v 2 Sheets-Sheet 1 HH I ' Was? 7 8 1941- L. D.ECKARD HULTIWAVE VARIABLE RESONATOR Filed Jan. 10, 1939- 2 Sheets-Sheet2 has the most eflicient ratio of Patented Aug. 19, 1941 UNITED STATESPATENT OFFICE 2,252,919 MULTIWAVE vamanna ansom'roa Lewis D. Eckard,Washington, D. 0. Application January 10, 1939, Serial No. 250,238 6Claims. (Cl. 171-119) The present invention relates to the combinationof a new and useful multi-coil transformer with a single tuningcondenser to provide a multiwave variable resonator.

It is customary in the manufacture of all wave radio sets today toutilize three or four small coils.

-tion, like numerals or reference indicate similar parts in the severalviews and wherein:

There are usually four antenna coils, four interstage or R. F. coils andfour oscillator coils in the radio circuit. These all wave sets areequipped with the standard 350 mmfd. tuning condensers and suitablepadding and trimming condensers with a capacity 15 to 30 mmfd. The useof small padding and trimming condensers to align the circuits 'in theradio set, or bring the various coils in each stage of tuning into aresonant condition, prevents the utilization of the minimum capacity ofthe tuning condenser. This results from the fact that no matter whatcapacity range the tuning condenser has the 15 mmid. or 30 mmfd. paddingcondenser always must be taken into account. 4

Another object is to pro de a radio set which has only one inductancecoil per stage of tuning.

Another object is to provide an inductance coil for a radio set, eithera transmitter or a receiver, which is adapted to expand or contract tovary the inductance.

Another object is to eliminate the padding or trimming condensers nowused in all wave sets to align the circuits or bring about a resonantcondition.

A further object is to provide an electrical circuit arrangement whichutilizes the minimum capacity range of the tuning condenser.

Another object is to provide a radio set which gets greater wave bandcoverage per unit coil.

Still another object is to utilize in combination with the electricalcircuit of a radio, a coil which diameter of coil to winding length ofwire thereon.

Another object is to provide a more simplified and less expensiveswitching arrangement in an all wave radio set.

Another object is to provide a more simplified and less expensive wiringsystem for an allwave radio set.

Another object is to eliminate the paralleling andclose proximity of theradio frequency wires to the switching apparatus.

Other and further objects the invention will be apparent from thefollowing detailed description and as more particularly pointed out inthe claims.

and advantages of I trical circuit hookup Figure 1 is an elevation ofone of the inductance coils, partly in section, in expandedformandembodying the principal features of the invention,

Figure 2 shows the inductance coil partly in section and in contractedform,

Figure 3 is an end view of the inductance coil,

Figure 4 is a diagrammatic sketch of the elecwhen the inductance coil isexpanded,

Figure 5 is a diagrammatic sketch of the electrical circuit hookup whenthe inductance coil is contracted, and

Figure 6 is a diagrammatic sketch showing the electrical circuit hookupof the two end strands of ,the inductance coil when the inductance coilis in expanded and contracted form.

Referring now to the drawings and more particularly to Figures 1 and 2,the numeral Ill indicates generally a cylindrical coil or wire carryingmember of light Celluloid, hard rubber or the like. The coil III hasbeen spirally cut to provide a helical portion ll extendingsubstantially throughout the length of the said coil Ill, and

which is of such a flexibility that it can expand or contract; A cableof wire I! is disposed at one end of the coil l0 and is wound spirally pn the helical portion II. The cable I! is composed of wires'of equallength and equal diameter, and comprises the primary windings of thecoil and is shown as comprising two insulated wires of equal length anddiameter and two turns on the flexible helical portion ll of the coilII. This invention is intended to cover any number of insulated wires inthe primary windings and although it is preferred to have the wires incable form it is not necessary.

V A cable of wire I3 is disposed upon the helical portion ll of the coilIII at the other end thereof in spaced relation from the primarywindings l2. These windings l3 constitute'the secondary windings oi thecoil. As shown, the cable It comprises ten insulated wires of equallength 4 and diameter and ten turns on the flexible helical portion llof the coil ll, but the number of wires. may be changed withoutdeparting from thescope of this invention.

A solid, uncut portion ll of the coil II is disposed outwardly oi. theprlmary'windings l2 and is centrally apertured and proportioned tothreadedly engage the threaded end of the spindle I! which passescentrally through the coil In the drawings forming part of this applica-5 II. A nut is threadedly cooperates with the tlally half the length ofthe coil.

2 assault threaded end of spindle it to move the portion M one way orthe other along the said spindle. The spindle [5 does not movelongitudinah ly in this operation. This selective movement slightlychanges the inductance of the coil as it moves the wire turns in'cableform closer to or farther from one another, and is important in aligningup the circuits at the factory. Finasimich as there is one coil used perstage oi tuning, it is always necessary toadjust the var icus coils toobtain a condition oi resonance. llieretofore a padding or trimmingcondenser was used for this purpose. i'iiter the fine justment has beenmade the factory by suit ably changing the :inductc ce the coil to obtain. complete resonance he not i may be sealed so that it may not betampered with.

The spindle i5 is suitably anchored at the end carrying the portion. it.li'lliis the fillEEl stationary nd of the coil.

The spindle i5 is anchored at the other end thereof in the member il andpasses centrally through another solid uncut portion of hard rubbermaterial H! which is similar to the member M. Mounted on thecircrunierential surface oi the cylindrical portion i l a plurality oimetal studs it, Ell; ill, til; llil, till; it, ti l; 25, 26, it; ill;till, fla l, ill, til", 32, 32'.

The studs Lil, ill" members for the are the contact secondary circuit,each ends. The free ends of the wires of both primary and secondarywindings are preferably soldered to their respective brass studs and canextend centrally through the interior of the inductance coil so as to beout of the way. The studs can be molded into the plastic coil iii if itis desired to do so. The said studs are preferably small and recessedsome-what so that a better connection can be obtained with the contacts34 and 35, hereinafter referred to in greater detail. a

A cylindrical insulated member 33 is disposed outwardly of and aroundthe coil 'lll adjacent to the movable member I9 and extends substan- Themember 33 is rigidly supported by the chassis in any suitable manner. Aplurality of metallic spring bars or other conductor strips 34 aremounted on the inner surface of the member 33 spaced from the cable l3,and each conducting stop 34 contacts wire batting two pressed form,although a coil of other dimensions can be used. In its expanded formthe coil has a length of approximately 3 inches.

Outwardly of the chassis disposed a cable drum 36 which is suitablysupported by the said chassis and upon which is wound a light cable Ellwhich extends through the said chassis and longitudinally through thecoil ill and around the pulley member 38 which is mounted on the memberi i at the relatively fixed end of the coil ill. The cable after passingover the pulley $38 which is adapted to rotate extends longitudinallythrough the interior of coil ill and is suitably securely fillBCl to themember at the movable end of the coil ill. The ratio oi the diameter ofthe drum to the length of the cable erably such that a three-quarterturn of said drum Elli will completely expand or completely contract thecoil ill to put the members M or in operative position.

it is to be understood that the drawings show only one coil which isadapted for one of tuning. As pointed out there are usually three ortour stages of tuning. For example, there were an antenna, radiofrequency and an oscillator stage it would be necessary to have threecoils similar to the one shown and described. These :ee coils will besuitably ganged together so that a turn on the drum. cable lit willsimultaneously expand or compress the three coils, creating an allparallel or an all series circuit condition, as described. Lille threecoils expand the same amount and ii there is a resonant condition whenare their compressed term that resonant condition will be maintained asthey expand through exactly the same distance upon one turn of the drum35.

In case of interstage coils the secondary circult is in the grid groundcircuit throughout, and

a pair of brass knobs or studs, e. g. 2|, 20'. The:

studs 2|, 2!, 22' 2 l', etc., on the member I! contact the spring strips34 when the coil I0 is in a contracted or compressed form. This is bestshown in Figure 2 when the primary windings are in series and thesecondary windings are likewise in series. Figure 5 shows the electricalcircuit when coil III is compressed.

A'plurality of pairs of metallic strips or rings 35 are mounted on theinner surface of the member 33 spaced from said metallic strips 34. Thestuds on the member I! contact the rings 35 when the coil I0 is in anexpanded form as shown in Figure 1. The electrical hookup for thisexpanded coil condition is shown in the wiring sketch of Figure 4. Inthis position oi: coil [0 the primary windings secondary windings arelikewise in parallel.

The 0011- I I has preferably a diameter 01' 1% inches and a. length of1% inches in its comthe primary is in the plate circuit of the previoustube and 13' plate potential and is adaptable to any oscillator circuit.

Figures 4 and 5 more clearly show the wire connections diagrammatically.In Figure 4 the primary windings of the coil in is in the antennagroundcircuit. In the secondary winding there is a parallel wiring conditionas follows: studs 20, 2], 22, 23, 24, 25, 26, 27, 28 and 29 areconnected together; studs 20', 2|, 22', 23', 24', 25', 28', 21', 28' and29' are all connected together. Stud II is connected to the grid G, andstud 29' is connected to the ground.

The efllciency of the coil number of turns of wire of diameter are usedin by an example.

On the basis of a. hundred turns of wire on four coils each having adiameter of 1% inches and a. length of 1 inches, note the following:

wherein an equal equal length and equal parallel can best be shown ppying the formula l l 1 LL1 L2 L3 E we have'lil' equaling 5 microhenrys.

I! ten coils are used each having the same num- V ber ofwire turns, asin. the present invention and using wire of equal length and equaldiameter, L

is found to be 2.6 microhenrys.

- ber of wire turns.

This computation does not take into account additional losses due to theunbalanced resistance of the various coils having an unequal num- -Whereall the coils have the same number of wire turns this additional loss isavoided as the current will divide itself equally through the variouscoils.

In Figure 4, the numeral 40 indicates a variable tuning condenser whichis preferably .in parallel with the grid ground circuit. The expansionof the coil i puts the primary windings l2 in parallel and the secondarywindings 13 in parallel to change the inductance of the said coil and toalter the capacity-inductance relation in the circuit and permits shortwave reception or transmission, since the inductance is low.

In other words, when the coil I0 is expanded the radio set receives highfrequency waves.

In Figure the wires of the primary winding II are shown in series withone another and the secondary windings are in series with each other. Inthis series relation the following wiring connections would result inthe secondary windings: would be connected to the grid G, 2| to 20, 2|to 22, 22' to 23, 23 to 24, 24 to 25, I! to 28, 26 to 21, 21' to 28, 28'to 29, and 29' to ground. When the primary windings of the coil are inseries and the secondary windings are in series the set receives longradio waves as the inductance is high and there is a correzpuondinginductance-capacity change in the cir- In Figure 6, the ignatedgenerally with the same numeral as the studs to which they areconnected. In the contracted position of the inductance coil the top endof strand 20 is connected to stud 20 and top end of strand 28 isconnected to stud 29. The lower end of strand 2' is connected to stud20' and the lower end of strand 29 is connected to stud 29'. Contact llcloses the circuit 20'-29 thus placing these windings in series.Contacts ll are insulated from each other and are each connected to oneof the rings .35 and these in turn are connected to the outsidecircuit, 1. e.,

the condenser, grid and ground.

In the expanded position of the inductance coil the studs II and 29 areparalleled by being connected to ring (top) while studs 20 and 20' areparalleled by being connected to (bottom) ring 35.

It is to be understood that in Figure 6 only two strands of wire havebeen shown to illustrate the electrical connections and that any numberof strarids may be used. The strands of wire should be of sufllcientlength to permit the full travel of the inductance coil from itscontracted to its expanded position.

After the various inductance coils have been aligned in the factory bythe.selective operation oi the nuts I to obtain resonance and the nutsI. have been suitably sealed one would operate the all wave s'et coveredby this invention as follows: if the broadcast band was desired theinductance coils would be compressed, Fig. 2: if the short wave band isdesired, the cable drum 3' is rotated approximately three quarters of aturn to a point where a suitable lug (not shown) stops its motion. Thecoils are now expanded and the inductance thereof is considerablyreduced. The coil I0 is. kept in alignment bythe strands of wire havebeendesin the usual manner to protect against stray magnetic fields orlines of .force and also against the overlapping of interstage magneticcouplings. It is intended to cover such changes and the applicantdesires to be limited only by the scope of the prior art and the claimsappended hereto.

I claim:

1. In a tuning circuit of an all wave receiving set;. an inductance coiladapted to expand or contract comprising; an expandible portionextending substantially throughout the length of said coil, primary andsecondary windings disposed on said expandible portion in spacedrelation, said primary windings comprising a plurality oi insulatedwires in coil form of equal length and diameter, said secondary windingscomprising a plurality of insulated wires in coil form of equal lengthand diameter, a relatively non-expandible movable portion having aplurality of spaced contact members on the surface thereof and disposedat one end of said coil, two series each comprising a plurality ofspaced apart contact members and each cooperating with said firstmentioned contact members, each of said first mentioned contact membersbeing connected to a free end done of theinsulated' wires in saidprimary and secondary windings, means re 1 sponsive to contraction ofsaid windings to interconnect the wires therein in series, meansresponsive to expansion of said windings to interconnect the wirestherein in parallel and manu-v ally operated means to expand or contractthe said inductance coil.

2. In a tuning circuit of an all wave receiving posed on said expandibleportion in spaced relaspindle II which passes through the endo! the wmember II.

There will be obvious changes in this invention, e. g., the inductancecoils .will be shielded tion, said primary windings comprising aplurality of insulated wires in coil form of equal length and diameter,said secondary windingscomprising a plurality of insulated wires in coilform of equal length and diameter, a relatively non-expandible movableportion having a plurality of pairs of spaced contact members on thesurface thereof and disposed at One end of the said coil, two serieseach comprising a plurality of spaced apart contact members and eachcooperating with said first mentioned contact members, each pair of saidfirst mentioned contact members being connected one to one free end ofthe other to the other free end of one said insulated wires, meansresponsive to contraction of said windings to interconnect the wirestherein in series, means responsive to expansion of said windings tointerconnect the wires therein in parallel, and manually operated meansto expand or contract the said inductance coil.

3. In a tuning circuit of an all wave radio receiving set havingantenna-ground and gridground circuits, an inductance coil adapted toexpand or contract comprising; an expandible portion extendingsubstantially throughout the length of said coil, primary and secondarywindings disposed on said expandibie portion in spaced relation, saidprimary windings comprising a plurality oi insulated wires in coil formof equal length and diameter and in series with the antenna-groundcircuit. said secondary windings comprising a plurality of insulatedwires in coil form of equal length and diameter, and being in thegrid-ground circuit, a relatively nonexpandible movable portion having aplurality of pairs of spaced contact members on the surface thereof anddisposed at one end of the said coil, two series each comprising aplurality of spaced apart contact members and each cooperating with saidfirst mentioned contact members, each pair of said first mentionedcontact members being connected one to one free end the other to theother free end of one of said insulated wires, means responsive tocontraction of said windings to interconnect the wires therein inseries, means responsive to expansion of said windings to interconnectthe wires therein in parallel, and manually operated means to expand orcontract the said inductance coil.

4. An inductance coil adapted to expand or contract a predetermineddistance comprising; said coil being wound on a form having anexpandible portion, primary and secondary windings disposed on saidexpandible portion in spaced relation and co-axial alignment, said formhaving a relatively non-expandible movable por 'tion disposed at one endof said coil, said movable portion having a plurality oi. contactmembers on the surface thereof, second contact means associated withsaid first mentioned contact members, and manually operated means. toselectively expand or contract said coil to change the cooperationbetween said contact members in such manner that the interconnectionsbetween said wire are changed.

5. An inductance coil adapted to expand or contract a predetermineddistance comprising; said coil being wound. on a form having anexpandible helical wire carrying member, primary and secondary windingsdisposed on said wire carrying member in spaced relation, said primaryand secondary windings each comprising a plurality or insulated wires ofequal length and diameter, said form having a cylindrical movableportion disposed at one end of the said coil, said movable portionhaving a plurality oi contact members on the surface thereof, secondcontact means associated with said first mentioned contact members, andmanually operated means to selectively expand or contract said coil tochange the cooperation between said contact members in such manner thatthe interconnections between said wires are changed.

6. An inductance coil comprising a plurality of strands of wiresinsulated from one another, said strands being helically wound on acommon expandiblc form, and means responsive to expension andcontraction of said form to control the connections between said wires.

8 n. ECKARD-

